26 U.S. Code § 6204 - Supplemental assessments

The Secretary may, at any time within the period prescribed for assessment, make a supplemental assessment whenever it is ascertained that any assessment is imperfect or incomplete in any material respect.

(b) Restrictions on assessment

For restrictions on assessment of deficiencies in income, estate, gift, and certain excise taxes, see section 6213.

These documents, sometimes referred to as "Private Letter Rulings", are taken from the IRS Written Determinations page; the IRS also publishes a fuller explanation of what they are and what they mean. The collection is updated (at our end) daily. It appears that the IRS updates their listing every Friday.

Note that the IRS often titles documents in a very plain-vanilla, duplicative way. Do not assume that identically-titled documents are the same, or that a later document supersedes another with the same title. That is unlikely to be the case.

Release dates appear exactly as we get them from the IRS. Some are clearly wrong, but we have made no attempt to correct them, as we have no way guess correctly in all cases, and do not wish to add to the confusion.